1. Field of the Invention
The present invention relates to an OFDM communication system, and more particularly, to the structure of an OFDM-based smart utility network (SUN) system capable of satisfying system requirements of IEEE 802.15.4 g.
2. Description of the Related Art
A smart grid is an intelligent power network that is being actively promoted in countries around the world, which aims at saving cost through efficient energy management, reducing less carbon through production and linkage of renewable energy, etc. Advanced countries such as U.S.A., Europe, etc. have been promoting various IT-based power network policies from the beginning of 2000 and even in Korea, national policies and strategies relating to the smart grid have been promoted since 2009.
An IEEE 802.15.4 g task group has focused on standardizing a smart utility network (SUN) physical (PHY) layer that is used as a wireless management network of the smart grid since May 2009 and has been proposing a wireless system technology capable of being designed to have low power consumption and providing high link margin characteristics to overcome a poor radio wave environment are being proposed.
Meanwhile, the Federal Communications Commission (FCC) has unanimously passed a proposal to permit use of a white space which is a non-use TV frequency band without a license in November 2008. In the case of the TV white space, standardization for a new service using the white space is being prepared in IEEE 802.11, 802.15, 802.16, and 802.22 as the most preferable frequency bands in a wireless communication.
Korean patent laid open publication Nos. 10-2004-0077279 and 10-2009-0057276 disclose “Apparatus and Method for Transmitting and Receiving Preamble of Ultra-wideband Communication System” and “Cost-efficient Preamble Structure for High-speed Communication of Packetized System”, respectively. The patent laid open publications disclose a method of discriminating a synchronization preamble primarily using a time domain signal and a channel estimating preamble primarily using a frequency domain signal from each other and forming the preambles of two domains, in configuring an OFDM transmission type preamble.
Further, Korean patent laid open publication No. 10-2006-0093224 discloses “MB-OFDM Transmitting/Receiving Apparatus and Method of Processing Signal Thereof”. Korean patent laid open publication No. 10-2006-0093224 discloses an interleaving data mapping technology capable of improving frequency diversity for the same data and diversity for adjacent data bits by performing a repeating operation, a shift operation, or a reverse operation for input data bits without increasing complexity in implementing hardware of the existing digital transmitting apparatus and receiving apparatus particularly in an OFDM signal processing method.
However, since the prior arts do not consider at all the high link margin characteristics to achieve low power consumption and overcome the poor radio wave environment required by the IEEE 802.15.4 g SUN standardization group, a new OFDM system structure capable of satisfying the requirements for the smart grid while minimizing an increase of system complexity has been needed.
Furthermore, the necessity of the OFDM system structures is markedly on the rise, such as a preamble structure, an OFDM symbol structure, etc. that are capable of utilizing the TV white space usable without a license at this point when the TV white space can be utilized and efficiently satisfying the requirements of the smart utility network (SUN) for the smart grid.